Check spot for particle counter



Jan. 2, 1962 G. E. GERHARDT 3,015,440

CHECK SPOT FOR PAR'IIICLE COUNTER Filed May 16, 1960 2 Sheets-Sheet 1 Jan. 2, 1962 G. E. GERHARDT 3,015,440 CHECK sPoT FCR PARTICLE COUNTER Filed May 16, 1960 27N F LT I/ C l i sa/ Y 2 Sheets-Sheet 2 BY M Mimi/r United States Patent O 3,015,440 CHECK SPOT FOR PARTICLE COUNTER Gerard Ernest Gerhardt, Plainfield, NJ., assignor to American Cyanamid Company, New York, N.Y., a corporation of Maine Filed May 16, 1964), Ser. No. 29,433 4 Claims. (Cl. 23S-92) This invention relates to a check spot for an electronic particle counter and more speciiically to an electronic counting system in which a display cathode ray tube shows the counted iield, including particles therein, and each counting pulse shows up' on the face of the display cathode ray tube as a bright check spot.

The counting of small particles is required in such diverse industrial fields as the determination of the number of particles of a pigment in a paint and a determination of the number of blood cells in a blood sample. In each instance, the particles may be visually counted by observation by selecting suitable magniiication, suitable iield sizes and actual visual counting by the operator. Such counting is usually referred to as manual counting. The count may be for a given area on a microscope slide using a standard reticle, or may be the number of items per microscope iield, or seen in any chosen area. Counting of this nature is tedious, and because of tedium the individual operator is apt to make errors.

Types of electronic devices have been devised. One such device is that described in United States Patent No. 2,936,953 dated May 17, 1960, entitled Apparatus for EX- tracting Particle Size Data, on application Serial No. 609,745 tiled September 13, 19526 by the present inventor, Gerard Ernest Gerhardt. The present application is a continuation-impart of said application 609,745. Said patent, 2,936,953, explains in more detail certain phases of flying spot scanners. Another circuit in which the present check spot may be used is described in United States Patent No. 2,803,496, T. C. Nuttall, August 20, 1957, Apparatus for Counting Objects.

in flying spot Scanners, it is convenient to incorporate a display cathode ray tube upon which is displayed the raster corresponding to the signal picked up from the canning system in which the presence of particles to be counted is visually represented.

Because the particles may vary in size and may have re-entrant configurations, and becauseof the possibility of electrical errors developing,7 in this system, it has now been found that a spot of increased intensity may be incorporated in the pattern shown on the face of the display cathode ray tube, which spot corresponds to counting pulses. Conveniently, but not necessarily, such spots are formed from counting pulses ahead of a gating system which provides for the counting of individual fields. Thus, it is convenient to have the target picture shown on the display cathode ray tube show counting pulses continuously by bright check spots, but the counting circuits count the spots on a single, individual field. This is conveniently accomplished by having a display cathode ray tube connected synchronously to the circuits of the scanning cathode ray tube with an ampliiied multiplier phototube output connected to the control grid which thus gives a display of the target scanned; and having the counting pulses feed through an amplifier to give a short negative pulse to the cathode of the display' cathode ray tube, and as the cathode goes more negative a stronger pulse of electrons is fed to give a brighter spot on the screen of said display cathode ray tube. The counting and the scanning circuits are thus completely separated and without influence on each other. lf suitable buffers are used to prevent interaction, both kinds of information can be applied to a single element of the display cathode ray tube.

falce* Such a check spot is particularly advantageous in working with particles of diterent sizes in which the counting can be adjusted to include only particles having over specilied dimensions, and thus there is a double check on the size of the particles being counted; one from the setting of the minimum size, and another one from the visual interpretation of the check spots against the particular particles being counted.

Further, if for any reason a missed count or a double count is occurring, the situation is immediately apparent to the operator.

In accordancel with the conventional practice, the details of the particular circuit elements are not here shown as these are well known to those skilled in the art. Suitable power supplies, bias resistors, coupling condensers, etc., as are understood by those skilled in the art, are necessarily used but are not a unique part of the present invention.

Obviously, Where lgated ampliiiers or other amplifiers are described, such ampliers may be incorporated with other operations, or a particular amplilier may in fact have a gain of less than one, if adequate gain is incorporated into associated components. Without being limited except as set forth in the accompanying claims,

one embodiment of the present invention is shown in greater detail in conjunction with the accompanying drawings in which:

FIGURE 1 shows a block diagram of the optics and electronics of the check spot incorporated in a particle counter.

FIGURE 2 is an enlarged diagrammatic View of the monitor cathode ray tube.

FIGURE 3 shows the potentials of the cathode and control grid of the display cathode ray tube during a particle count and display.

FIGURE 4 shows the scanned field on the display cathode ray tube, showing particles and the check spot.

In FIGURE 1 is shown a scanning cathode ray tube 11 which is of a high intensity, short persistence type. To drive and cause a ilying spot to scan a raster on the face of the scanning cathode ray tube, the sync generator 12 drives the iield and line sweep generator 15. The eld and line sweep generator 1S controls the deflection circuits for eld and line of the scanning cathode ray tube 11 and the display cathode ray tube 16. Separate iield and line sweep generators may 'be used if the deflection systems of the scanning cathode ray tube 11 and the display cathode ray tube 16 are not conveniently adapted for parallel operation. Either electrostatic or electromagnetic deliection may be used, but preferably the tu es have similar characteristics as regards deection requirements. The sync generator 12 also feeds pulses to a delay line 13 which feeds pulses through a sync separator 14, which sync separator 14 in turn feeds back to the sync generator 12. Thus, the sync generator period is equated to the delay line period by this arrangement.

A blanfking generator 17 is also driven by the sync generator 12 and blanks the return trace on the scanning cathode ray tube 11.

An image of the raster on the face of -the scanning cathode ray tube 11 is focused -by lens 18 on a target 19. The target 19 is conveniently a microscope slide on which the sample to be counted is placed. The target may also be a photograph of the sample. For blood cell counting, conveniently, the lens system 18 is a compound microscope. Beyond the target 19 is a condenser lens 20, which focuses the image of the scanning raster and the superimposed target on a multiplier phototube 21. The multiplier phototube 21 is connected through a suitable battery 22 and load resistor 23 to a video preamplifier 24 through an equalizer Z5 to -a video ampli-fier 26. Other photo- Aelectric detectors may be Y yticlesiwhich block the spot.

tubes are among the most sensitive and economical. The output of the video amplifier is connected to the control grid 27 of the display cathode ray tube 16. The signal from the video a-mplifier 26 contains blanking information as Well as video information, which shows each interruption of the spot as it traverses each line in the 4 scanning cathode raytube 11. Thus, the display cathode ray tube lv'shows each individual line inthe field of the scanning cathode ray tube 11 with interruptions for par- Thus, the display cathode ray tube 16 shows as its picture the information concerning particles on the 'target 19.

Also connected to the output of the video amplifier 26 is a shaper 2S which sharpens the pulses from the videoamplifier. v It -is desired that in the counting circuits the y rise time of each pulse .be at a minimum. Because the spot on the face of the scanning cathode ray tube 11 has v its image cut ofi gradually as the spot passes behind an opaque area on the target as a function of the part of the spot blanked out, the rise time of the video pulse from the multiplier phototube 2l may be longerY than desired. The Shaper and equalizer sharpen the pulses. The output from the Shaper 28 passes to the delay hue .13, 'and down the delay line, where it is delayed for the period of one sweep, through the sync separator 14, and to the control of the first gated amplifierV 29.

.'The output from the Shaper. 28. goes to `a first. gated Iamplifier 29. The delayed Videofrom sync separator le .corresponds to the preceding line and comprises the `controly signal for the first gated amplifier 29, so that the rfirst gatedampliiier only passes a pulse which corresponds to a signal from one line of the raster which does not correspond to the signal from the preceding line on the raster. Thus, the preceding line is generated electroni.- cally and acts as a gating signal to indicate that a particular particle has already been counted. The output from the first grated amplifier 29 is fed through `a differentiate! 30 and a clipper 3l where it emerges as a sharp pulse corresponding to the leading edge of each Video pulse. The pulse corresponding to the trailing edge is negative and does not pass. As the output goes to the first flipflop circuit 32, it produces a squarewave lpulse at the output of the flip-flop circuit which is fed as the control for ya second gated amplifier 33, which holds the. gate of the second gated amplifier open until another positive pulse is applied to the input of the first flip-flop 32. The signal for the second gated amplifier 33 is a sharp pulse produced from the trailing edge of the undelayed video rpulse from the shaper 28, after. passing through a second differentiator` 34. The count pulse from the second gated amplifier 33l is passed through `a short delay '35 into a `butir'er 36 with a resulting positive pulse which is slightly going pulse at the Vcathode 3S of the display lcathode ray tube 16. A negative pulse to the cathode 3S acts the same as a' positive pulse to the grid and causes a lbrightening of the raster which appears as a bright spot corresponding to the counting pulse.

The output from the second gated amplifier 33 is yalso fed to the third gated amplifier 39 from which the outu put is fed to a scaler 40. The Scaler may be a conventional pulse `counting device set to count the number of pulses supplied through the third gated amplier 39. The controlvto the third gated amplifier is arranged to open the fgate for .the vduration of a single field.

used, but multiplier photo-4 Preferably, the linesl in the field lare sequential. and each field is completerV "This is in contrary distinction to the ordinary TV circuit in which interlaced lines from sequential fields are normally used.

While other circuits may be used, a convenient control for the third gated amplifier consists of a fourth gated amplifier 41 fed by the field sync signal from the sync generator which feeds a second flip-flop 42, which second flip-flop furnishes a control to the third gated amplifier39 and a third fiip-flop 43. Manual resetting is provided by a reset 44 which is conveniently a ground reset button which is normally closed. When the reset button is pressed, it opens the grid returns of the second half of thefirst iiip-fiop, the second half of the second fiip-iiopf and the first half of the third dop-liep. in the normal condition, the second half .of the ytube of the third flip-flop is conducting, as is the second half of the tube ofthe second flip-dop. The plates of both being more negative, the control grids of the fourth gated amplifier and of the third gated amplifier are both closed and no signals reach the sealer and the field sync input signals are not amplified. The first flip-iop is likewise grounded and operates normally. When the reset button is Vpushed to open the grid returns, the first half of the tube of the third fiip-fiop receives positive voltage from B+, this half therefore starts to conduct throwing a negativefvoltage onthe grid ofthe second half ofthe tube which is cut ofi; the tube is flipped. The cut off of this vsecond halt' of the tube puts a more. positive voltage on the control grid of the fourth gated amplifier and therefore'opens this fourth gate so that the field sync signal is amplified. However, yas long as the reset button is held in, the grid return of the second half of the tubeof the second flip-flop and the fiip-fiop is ineffective. As soon as the reset button is released, the grid return of the second half of the second flip-flop is closed, and the next fieldy sync pulse is amplified; the positive pulse causes the second flip-tldp toV flip, the first half of the tube becomes conductive, and the second half of the tube is cut 0E.

VThe plate of the second half becomes more positive and impartsl its voltage to the gate'of the third gated ampli- Y fier leading to 'the'scalen Hence, counting pulses during `the Whole of the lnent field scan are passed through to the sealer. When the" field scan has gone through one Vfield, thernext field scan pulse passes through to the secamplifier, and closing it. v

Thus, the scaler'shows the count for the. one field only.

As is obvious to those vskilled in the art, pentode tubes are very convenient for theA gated amplifiers and double triodesfor therfiip-ffop tubes.` However, transistors or other tubesiand tube circuits may be used for components of the individual'electronic devices shown in the blocks which represent'conventi'onalelectronic' circuitry known 'to those 'skilled in the electronic particle counting art.

The newy check spot systems can be used with other counting circuits, other systems to insure counting of a single' field, andl other scanning systems in whichthe count pulse has the proper temporal relationship with the intercepts of the particle being counted.

I claim:

l. In a particle counting device for counting particles above a predetermined size comprising: a holder adapted to hold aV sample 'ina predetermined plane, raster scanning means optically associated with said plane, a photoelectric detector forproducing electric pulses at video frequency as' dscrete'pa'rticles in the plane lare scanned, an electronicfcoun'ter therefor including a main delay circuit having a delay period equal toa multiple of a horizontal f scanningperiod, feedbackvmeans fromr said main delay circuit tothe 'rasterl scanning means to insure synchronous operation, and triggered gating means actuated by the output of the delay circuit to form a coincidence-anticoincidence circuit, counting taking place only when no pulse from the delay line output encounters the triggered gating means, the improvement which comprises a display cathode ray tube which shows the scanning raster from a signal from said photoelectric detector and the particles being counted, and means fed from said counting circuit to cause the display tube to show -a brightened pulse for each counting signal at each scan of the raster.

2. Iln a particle counting device for counting particles comprising: a holder adapted to hold a sample in a predetermined plane, raster scanning means optically associated with said plane and a photoelectric detector for producing electric pulses at video frequency in which the signal is affected by particles in a sample in said holder, and a counting circuit, the improvement which comprises a display cathode ray tube which shows the signal and the eects of particles on the signal, thus showing the particles on the face of said display cathode ray tube, and a feed from the counting circuit which causes a brightened pulse adjacent each counted particle corresponding to the counting pulse, wherein a visible brighttened spot indicates eachcount, thus showing that the counting circuits are counting each specic particle, and that no particles are being counted twice.

3. In a particle counting device for counting particles comprising: a holder adapted to hold a sample in a predetermined plane, raster scanning means optically associated with said plane and a photoelectric detector for producing electric pulses at video frequency in which the signal is affected by particles in a sample in said holder, the improvement which comprises a means for feeding a signal from said photoelectric detector suitably amplified to the control grid of a display cathode ray tube thereby visually showing said signal and the particles in a sample, and means electrically connecting the cathode of said cathode ray tube to a counting circuit, whereby the cathode goes more negative at a time corresponding to each counting pulse, hence brightening the display for a short fraction of a scanning line corresponding to each counting pulse.

4. The method of checking visually a particle count comprising: passing a flying spot over a eld to be counted, photoelectrically picking up a signal corresponding to the presence or absence of a particle at each part of said field, displaying the picked up signal on the face of a cathode ray tube, and simultaneously displaying a brightened spot adjacent the image of each particle corresponding to a count impulse for that particle.

References Cited in the le of this patent UNITED STATES PATENTS 2,948,470 Berkley et al. Aug. 9, 1960 2,959,349 Marsh et al Nov. 8, 1960 

